MULTIPLE INPUT MULTIPLE OUTPUT BY SAIKIRAN PANJALA

MULTIPLE INPUT MULTIPLE OUTPUT

By

XXXXX (12XXXXXXX)

Under the guidance of XXXXXX, XXXX Lecturer

1. INTRODUCTION

MIMO Systems:• use multiple inputs and multiple outputs from a single

channel.

SPATIAL DIVERSITY AND SPATIAL MULTIPLEXING

1. Spatial Diversity• Signal copies are transferred from multiple

antennas or received at more than one antenna

2. Spatial Multiplexing• the system is able to carry more than one data

stream over one frequency, simultaneously

Why MIMO....?

1. There is always a need for increase in performance in wireless

systems

• Significant increase in spectral efficiency and data rates

• Wide coverage, etc.

2. Wireless channel that we are using is very unfriendly

• Suffers from Co–channel interference and signal level fading

• power falls off with distance

MIMO System solutions

1. By using Multiple Output Multiple Input (MIMO) systems

• Diversity gain mitigates the fading and increases

coverage and improves QOS

• Array gain results in an increase in average receive SNR.

2. Spatial Diversity and Spatial Multiplexing can be

conflicting goals

Spatial Multiplexing

1. MIMO channels can be decomposed into a number of R

parallel independent channels → Multiplexing Gain

• Principle: Transmit independent data signals from different

antennas to increase the throughput, capacity.

MEMO capacity on fading channels

1. The capacity increase can be seen by comparing MEMO systems

with SISO, SIMO, and MISO systems

• SISO:capacity is given by Shannon’s classical formula:

Where B is the BW and h is the fading gain

• SIMO (with M transmitting antennas), the capacity is given by [2]

)21(2log hsnrBC

)1

21(2log

m

n nhsnrBC

MEMO capacity on fading channels

• The capacity for MIMO systems can have the following forms (Assuming Tx antennas = Rx antennas = N):

A) If the channel is not known at the transmitter:

Where Es is the total power, σ2 is noise level of AWGN

B) If the channel is known at the transmitter

)2

21(2log nhNsENC

N

n nhnEC

1

)2

21(2log

MEMO capacity on fading channels

• With the channel known at the

transmitter, the total power

allocation the each channel

will be based on watterfilling.

Where σN2 = σ2 / h│ n

2│

Average capacity of a MIMO Rayleigh fading channel

0

5

10

15

20

25

30

35

40

45

50

55

60

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

SNR [dB]

Ave

rage

Cap

acity

[bits

/sec

/Hz]

N=1 M=1 N=2 M=1 N=1 M=2 N=2 M=2 N=2 M=4 N=2 M=6 N=4 M=4 N=8 M=8

Spatial Diversity

• Improves the signal quality and achieves a higher SNR at the receiver-side

xiyi

MIMO Diversity and Reliability

The performance improvement in SNR and error probability for MIMO can be compared with SISO, SIMO, and MISO

The detailed calculation for SNR and Pe is shown in [1] SISO:

Receive Diversity (SIMO):Ninxhy iii ,2,1,

N

i

hSNRhSNR 2)(

21

1SNRPe

nhxy

22

2

)( hSNRnE

hxEhSNR and

NSNRPe

21

1and

MIMO Diversity and Reliability

• The values for SNR and Pe for: Transmit Diversity (MISO):

• Transmit/Receive Diversity (MIMO): The received signal at antenna i will be:

ijij

M

ji nxhy

1

22

)(},min{

HSNRHSNRMNHSNR

MSNRPe

21

1

nxhy j

M

j

j 1

M

j

jhSNRhSNR1

2)( and

MN

MNSNR

Pe

},min{21

1and

Conclusion

• The capacity of Receive or Transmit Diversity grows

logarithmically with the number of antennas

• Capacity of MEMO increases linearly with the number of

antennas

• Using Spatial Diversity:

• The SNR increases and Pe decreases when using MIMO

References

[1] MIMO Architecture for Wireless Communication: Intel Technology Journal, vol. 10, Issue 02, May 2006

[2] MIMO Systems and Transmit Diversity,www.comm.utoronto.ca/~rsadve/Notes/DiversityTransmit.pdf

[3] R.A. Carrasco, Space-time Diversity Codes for fading Channel,Staffordshire University